This invention relates to an apparatus for obtaining, by using a radiation source and a radiation detector, the two-dimensional distribution of the transmission or absorption of a radiation to an object to be examined, and particularly to an apparatus so arranged that the radiation passed through the object is measured plural times while the relative, positional relation between the radiation source and radiation detector is being changed, and stored as digital images, and a linear arithmetic operation is performed on a set of data obtained from radiations passing a point within the object to be examined, thereby obtaining a cross-sectional image on a given cross-section approximately parallel to the radiation detector plane of the object to be examined.
The apparatus for photographing a cross-sectional image of human body by using radiation is well known. The conventional radiation cross-sectional image measuring apparatus photographs an image on a cross-section at a depth of human body by permitting usually a film to be exposed multiple times to the radiation of images while the relative positional relation between the radiation source and the radiation detector such as a film is being changed. This apparatus, however, obtains only a single cross-sectional image by a sequence of radiation emissions, and therefore for an unknown depth at which a focus exist, the human body is unnecessarily exposed to radiation.